Redes neurais e suas aplicações em calibração multivariada

Neural Networks are a set of mathematical methods and computer programs designed to simulate the information process and the knowledge acquisition of the human brain. In last years its application in chemistry is increasing significantly, due the special characteristics for model complex systems. The basic principles of two types of neural networks, the multi-layer perceptrons and radial basis functions, are introduced, as well as, a pruning approach to architecture optimization. Two analytical applications based on near infrared spectroscopy are presented, the first one for determination of nitrogen content in wheat leaves using multi-layer perceptrons networks and second one for determination of BRIX in sugar cane juices using radial basis functions networks.

Sistemas interfaceados de análise por injeção em fluxo e eletroforese capilar (FIA - CE): desafios, aplicações e perspectivas

A review about the state-of-the-art of flow injection analysis (FIA) -- capillary electrophoresis (CE) systems is presented. The basic principles of flow injection and capillary electrophoresis are briefly revised. The main aspects of the FIA-CE hybridization, including advantages and shortcomings, are discussed. Some applications involving all different designs are also presented. This review covers the literature from 1997 up to 2000.

Células a combustível de baixa potência para aplicações estacionárias

A paradigmatic shift in developing fuel cell for stationary applications has been occurring in the last ten years. Previously, 100 kW class to a few MW class power plants were preferred but recently, the development has drifted towards units of only a few kW. The motivation is the present market situation, which favors disperse residential electric power generation from natural or liquefied gas. Membrane-type fuel cells are very promising for this application, due to their present state of development in the automobile industry. More recently, small ceramic fuel cells (SOFC) has also been found to be adequate for this application. Considering a family of 4 members, 1 kW (electric) units seem to be optimal for individual residences. This presentation discusses briefly the Brazilian scenario with respect to these units.

Biossurfactantes: propriedades e aplicações

Chemically synthesized surfactants are widely used for many purposes in almost every sector of modern industry. Surface-active compounds of biological origin (biosurfactants) have been gaining attention in recent years because of some advantages such as biodegradability, low toxicity, diversity of applications and functionality under extreme conditions. Microbial biosurfactants are useful in bioremediation of water and soil, enhanced oil recovery, and in many formulations of petrochemical, chemical, pharmaceutical, food, cosmetic and textile industries. The importance of biosurfactants, their characteristics and industrial applications are discussed.

Terapia fotodinâmica: aspectos farmacológicos, aplicações e avanços recentes no desenvolvimento de medicamentos

Photodynamic Therapy (PDT) is a clinical procedure, which utilize a photosensitive compound and light. This is a new modality of treatment for cancer, aged related macular degenerescence (AMD), psoriasis, arthritis, arterial restenosis, etc which exhibits efficiency, less traumatic effects, low recovery time and few co-lateral effects. The first officially approved drug for PDT by the Food and Drug Administration (EUA) is Photofrinâ, which is applied for cancer. A new generation drug for PDT, Visudyneâ was recently approved to treat AMD; its photoactive compound is BPDMA, a benzoporphyrin mono-acid derivative (chlorin-type molecule). A concise history, technical information and some drugs for PDT are reported.

A quimiluminescência como ferramenta analítica: do mecanismo a aplicações da reação do luminol em métodos cinéticos de análise

Relevant aspects of proposed mechanisms of the chemiluminescent reaction of luminol are presented and commented to emphasize its perspectives for kinetic analysis. A careful search for analytical applications of this reaction is discussed in order to point out new trends of the studies. Kinetic analysis using the luminol reaction is proposed to be a very attractive due to the good performance of the reaction in analytical applications and the positive characteristics of kinetic analysis, such as low cost and sensibility. It is pointed out that kinetic analysis using the chemiluminescent reaction of luminol should be encouraged.

Tendências em modificação de eletrodos amperométricos para aplicações eletroanalíticas

The most relevant advances on the analytical applications of chemically modified electrodes (CME) are presented. CME have received great attention due to the possibility of electrode surface modification including chemisorption, composite generation and polymer coating. In recent years, the interest in CME has increased overall to improve the sensitivity and selectivity of the electroanalytical probes, considering the electron mediator incorporation and the new conducting polymers development. The general procedures employed for the electrode modification and the operational characteristics of some electrochemical sensors are discussed.

Síntese e reatividade de azaindóis: aplicações na preparação de moléculas de interesse biológico

Synthetic methods used for the preparation of azaindoles are described in this article. Applications in the preparation of bioactive molecules are given: synthesis of substituted 6-azaindoles as benzodiazepines receptor ligands, substituted 7-azaindoles as dopamine D4 ligands and preparation of an olivacine analogue.

Aplicações eletroanalíticas com eletrodos de prata confeccionados a partir de CDs graváveis

This paper presents a new way for the construction of silver electrodes utilizing recordable CDs. The new electrodes were explored for the quantification of chloride (by potentiometry/FIA), cyanide (by amperometry/FIA) and for lead analysis (by square wave voltammetry). For the flowing measurements, a digital multimeter, connected to a microcomputer (via RS 232 interface) was used to collect directly the potential signal (for Cl- measurements) or to take the output signal from a potentiostat (for CN- measurements). The square wave voltammetry analysis was performed in a commercial instrument. The results shown good performance of the new electrodes and the detection limit (s/n = 3) attained for these three analytes were: 0.2, 50, and 200 µg L-1 for Pb2+, Cl-, and CN- respectively.

Sucroquímica: síntese e potencialidades de aplicações de alguns derivados químicos de sacarose

The interest on the use of sucrose as raw material increased in the last years. In this work, the synthesis and applications of sucrose derivatives as esters, ethers, and other products are discussed in a concise manner aiming to presenting the sucrochemistry as a promising field in organic chemistry from a rather accessible, low-priced, ecological, and renewable source.

Microemulsões: estrutura e aplicações como sistema de liberação de fármacos

Depending on formula composition, microemulsions may be used as a vehicle for drug administration. In this work the main applicable parameters used in the development of pharmaceutical microemulsions (ME) are analyzed. The conceptual description of the system, theoretical parameters related to formation of internal phases and some aspects of ME stability are described. The pseudo ternary phase diagram is used to characterize ME boundaries and to describe different structures in several regions of the diagram. Some applications of ME as drug delivery systems for different administration routes are also analyzed. ME offer advantages as drug delivery systems, because they favor drug absorption, being in most cases faster and more efficient than other methods in delivering the same amount of drug.

Especiação analítica de compostos de arsênio empregando métodos voltamétricos e polarográficos: uma revisão comparativa de suas principais vantagens e aplicações

This paper provides a review on voltammetric and polarographic methods for the speciation analysis of inorganic and organic arsenic compounds in different matrices. A discussion on the main advantages of electroanalytical methods in comparison with other analytical methods employed for arsenic speciation is presented. The mechanistic aspects of the most relevant techniques employing cathodic and anodic stripping voltammetry as well as polarographic methods published in the last twenty five years are summarized and discussed. The bibliographic references cited in this work were selected from the Web of Science (published by the ISI) and the main journals of analytical chemistry.

Aplicações sintéticas de lipases imobilizadas em polímeros

The application of biocatalysis is a promising field related to new technologies for organic synthesis. The development of immobilization techniques is very important due to the multiple or repetitive use of a single batch of enzymes and the ability to stop the reaction rapidly, at any stage, by removing the enzymes. In most cases, after immobilization, enzymes and microorganisms maintain or even increase their activity and stability. This work presents an overview of the common methods for lipase immobilization in polymers and applications of these systems to obtain compounds of synthetic interest.

Sínteses química e enzimática de peptídeos: princípios básicos e aplicações

This review begins with a brief discussion of the biological importance and chemical features of peptides. A description of the existing synthetic methods follows with emphasis on the basic aspects of the chemical and enzymatic syntheses. Techniques used to purify and characterize the synthesized peptides are also discussed. Finally, a few applications of the final products in chemistry, biochemistry, immunology and medicine are presented, such as identification and quantification of naturally occurring peptides, inspection of structure-activity relationships, therapeutics, development and/or improvement of analytical techniques and search for new vaccines.

Voltametria de onda quadrada. Segunda parte: aplicações

The aim of this work is to discuss some selected applications of square wave voltammetry published in the last five years. The applications focused here cover several electroanalytical fields such as: determination of pesticides; molecules with biological activity; metals and other environmental pollutants. Special attention is given to the work developed in the Grupo de Materiais Eletroquímicos e Métodos Eletroanalíticos - IQSC - USP concerning the utilization of square wave voltammetry, with different kinds of electrodes, for the determination of pesticides in natural waters and active principles in pharmaceutical formulations. The new methodology is simple, fast and sensitive when compared with the traditional ones such as chromatography and spectrophotometry. The satisfactory results obtained provide alternative procedures for the quality control of drugs and the monitoring of pesticides in natural environments.